[3 + 3] Annulative Functionalization Approaches to Poly-Functionalized 8-Acylindolizines, 8-Enylindolizines, and Indolizine-Coumarin Hybrids

Synthetic efforts to expand the indolizine chemical space via an annulative functionalization strategy are described. Cs₂CO₃-promoted [3 + 3] annulations under mild reaction conditions enabled facile decoration of a number of functional groups at the pyridine moiety by way of a domino <i>N</i>-alkylation-intramolecular aldol condensation procedure to afford a wide range of novel indolizines such as 8-acylindolizines, 8-enylindolizines, and coumarin-indolizine hybrids.